Optical information processing systems conventionally utilize a light source and a detector providing a photo-optical path. These systems are generally designed to acquire data about a medium placed within the photo-optical path and, for example, can be used for position sensing, color determination, and for measuring reflectivity and transmissivity of the medium.
Optical intensity mapping devices that sense variations in optical density or light scattering of a medium are used in analytical chemistry for measuring critical micelle concentration by detergents, fatty acids and phospholipids. Similar photodetector instruments have been applied to analytical biochemistry for example, in blood clotting time measuring apparatus. These apparatus generally employ a sensor for determining increases in optical density and provide a signal proportional to the optical properties. Typical devices for optical blood analysis are illustrated in U.S. Pat. Nos. 4,876,069; 4,720,787; and 4,775,237.
With regard to devices for monitoring blood coagulation, plasma from a blood specimen is usually combined with a prescribed amount of chemical reagents which precipitate clotting. As the clotting progresses, the optical density of the specimen increases. A graphic history of the specimen's optical density over time is referred to as a "clot signature." Characteristics of a patient's clot signature provide clinicians with diagnostic information about the patient's medical condition.
Currently, the process for the measurement of blood coagulation is subject to variables which must be controlled or standardized if the measurement process is to yield valid and consistent results. In regard to optical coagulation sensing instrumentation, the apparatus is calibrated by combining reagents with a sample of control plasma or standard solution and then comparing the resulting "clot signature" with a prescribed norm or benchmark. However, if the control plasma and/or patient plasma produces an irregular or abnormal "clot signature," it is difficult to isolate the source of this inconsistency. The problem may lie in the composition of the control plasma, the reagent solutions, the hydraulic system delivering the reagent solutions or the photodetector system. The diagnosis of the irregularities in the test results can be expensive and a time-consuming procedure involving for example, the verification of the composition of the control plasma, the reagent solutions or confirmation as to the accuracy of the hydraulic system or photodetector system. Frequently, a technician must be summoned to examine the apparatus and to determine the source of the problem. This often results in "downtime" or a cessation of a medical facility's blood analysis program until the malfunction is remedied. Furthermore, it is impractical for hospitals to purchase redundant blood analysis apparatus in view of the expense involved or to maintain an oversupply of reagent solutions in view of their perishability.